Can I save these brake calipers?

I wouldn't worry much about those calipers. They are the same from all 94-04 GT/Cobra rear brakes. I am sure you can pick up a set of them for 50-60 shipped at the most.

 

They can prolly be saved. The determining factor will be the amount of rust and pitting that is on the piston and inside the bore. Ive never rebuilt any rear brakes, so the parking brake setup is gonna make it a little more of a pita than a front caliper. That leads me to my next question. Are you sure the parking brake isnt causing the caliper to be stuck? Id say slap it in a vise and work the parking break mechanism. Dont be suprised if this causes the whole piston to pop completely out, which you would want anyways if you are gonna rebuild it. If it doesnt, use compressed air with a blow nozzle, or if that fails, screw a zerk fitting in place of the bleeder and pump in some grease. Use sandpaper or emry cloth to clean up the piston and the bore. The few rear brakes that ive taken apart just to see how they worked, have this screw type deal that pushes on the back of the piston when the lever is moved. Its always nice to be able to take something apart to see how it works and not worry about putting it back together. Be sure to put something in between the piston and the caliper, like a piece of wood, so the piston doest fly outand slam into the other side of the caliper. Oh yeah, lube the new seals with brake fluid also.

 

I replied on FB about using Marvel Mystery Oil. You can get by the gallon at the parts house.
It's a great penetrate. Soak the whole thing or just a dribble on the edge of the moving parts, let it set for a day then begin working it loose.
Those threads for the brake line look pretty boogered up though

 

Your stock rear calipers are the same ones

 

Question is, why would you want to when a replacement (from Ford core) is available from AutoZone for like 45 dollars a pop (90 before returning the core)

 

Ya, kinda no brainer. Just replace, brakes are important.